The purpose of this study is to help determine the functional role of the arcuate nucleus of the hypothalamus in reproductive neuroendocrine mechanisms. The experiments outlined in this proposal will 1) focus on the role of the arcuate nucleus and preoptic area in steroid feedback mechanisms in the male and female animal, 2) study the role of these hypothalamic structures in the induction of LH surges and 3) study the role of dopamine in the control of gonadotropin secretion. The animal model to be used in this study will be the hamster which was treated neonatally with monosodium glutamate. On the basis of studies in our laboratories for the past several years, this type of treatment results in a specific lesion of the arcuate nucleus. Some of the techniques and procedures to be used on animals with this lesion include: hypothalamic deafferentation, electrochemical stimulation of the hypothalamus, electron microscopy, measurement of plasma and pituitary levels of LH and FSH by radioimmunoassay and enzyme histochemistry.